Conventional rotation-angle sensors include a rotation-angle sensor utilizing a non-contact magnetic method, a rotation-angle sensor utilizing a contact-type mechanical method, and the like.
FIG. 21 is an example of a non-contact rotation-angle sensor as a first conventional example.
Two magnetic sensors 2 and 3 are arranged around a rotatable magnet 1. Output signals a and b whose amplitudes are different from each other are detected through the magnetic sensors 2 and 3 based on the rotation angle of the magnet 1. The detected output signals a and b are amplified by an amplifier 200 and the polarities of the output signals a and b are determined by polarity determination circuits 201 and 202. Then, digital output signals D1 and D2 are created based on the result of polarity-determination and the result of determination by an angle determination circuit 203, and the rotation angle of the magnet 1 can be calculated.
FIGS. 22A and 22B are each an example of a contact-type rotation-angle sensor as a second conventional example.
FIG. 22A is a schematic configuration of a potentiometer 250 used for a switch of a camera as a contact-type rotation-angle sensor. A switch main body 252 is contained only in a camera case 253 without a rotation dial portion 251.
FIG. 22B is a circuit configuration including a variable resistor 254 in the switch main body 252.
The electric potential of a contact portion 255 between the variable resistor 254 over terminals V1 and V2 and a mechanical rotation axle is detected as an analogue output signal. Thus, the rotation angle of a mechanical switch is calculated.
Patent Document 1: Japanese Patent Laid-Open No. 9-6527
Patent Document 2: Japanese Patent Laid-Open No. 2000-46536
Patent Document 3: Japanese Patent Laid-Open No. 2001-114116
Patent Document 4: Japanese Patent Laid-Open No. 2002-243407
Patent Document 5: Japanese Patent Laid-Open No. 2004-239672